Bituminous pavement rejuvenator



De 7, 1965 E. w. M GOVERN BITUMINOUS PAVEMENT REJUVENATOR Filed Oct. 26, 1962 RES/DUE TEMPE/7A TURE o C.

FIG.

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TIME AFTER APPL ICA T/ON MONTH5 INVENTOR.

EDWARD M4 M0 GOVERN Ms ATTORNEY GAL. /YD.2 7-76. 3

United States Patent OfiFice 3,221,615 BITUMINOUS PAVEMENT REJUVENATOR Edward W. McGovern, Pittsburgh, Pa., assignor to Koppers Company, Inc., a corporation of Delaware Filed Oct. 26, 1962, Ser. No. 233,276

2 Claims. (Cl. 94--23) This. invention relates to a method and composition for reconditioning bituminous pavements.

Bituminous pavements, for example, asphalt roads,

tend to harden, crack, ravel and generally deteriorate.

over a period of years and finally the road becomes unsatisfactory forfurther use. While the phenomena is not completely explained, it is believed the hardening of the asphalt roads over a period of years is due to a slow loss of volatile materials from the asphalt and to an oxidation of the asphalt itself (ultraviolet light particularly appears to promote oxidation). As the surface of the paving hardens, it cracks, thereby exposing more bituminous surface for oxidation; the cycle repeats; and the cracks deepen.

The paving industry thus is faced with the need for economically prolonging the useful life of a bituminous pavement and the need for economically repairing a badly cracked bituminous pavement. The problem may become vexious because curbing, drainage, and like lirnita tions may not permit a thickness change in the paving layer, as would be caused by placing a new overlay on the old paving. If a new overlay be placed on the aged pavement, the cracks in the aged pavement may cause cracks and. fissures to appear in the new overlay. There also exists the problem that vehicles may pick up loose materials from the overlay and cause a safety problem, particularly if the vehicles. be aircraft rolling on runways. Seals of coal tar pitch emulsion or asphalt emulsions or slurries, of course, are only temporary measures to protect the pavement surface.

It has now been found in accordance with this invention that bitmunious pavements which are in the process of becoming or have become dry and brittle through aging and weathering may be revitalized by applying thereto a composition which is derived from coal tar and comprises a mixture of di-, triand tetracyclic aromatic compounds and their alkyl homologs containing lower alkyl groups together with a significant amount of phenolic and hydroxy derivatives, said mixture having a specific gravity at 25/25 C. of at least 1.08, an initial boiling point of at least 180 C., and a, continuous, boiling range to at least 300 C., 70-40% by volume of the material remaining as residue at 300 C., and the distillate to 300 C. having a minimum specific gravity at 25/25 C. of about 1.025.

FIGURE 1 illustrates. the distillation curve. for the novel composition of this invention;

FIGURE 2 illustrates, the. depth that the composition will penetrate aged bituminous paving with the passage of time; and

FIGURE 3. illustratesthe extent of rejuvenation of aged bituminous paving as measured by the characteristic, penetration.

The novel composition of: this invention revives the 3,221,615 Patented Dec. 7, 1965 pavement without increasing the thickness of the pavement. The novel composition is believed to rejuvenate or prolong the useful life of bituminous pavements by plasticizing the binder. It has been found that the paving treated in accordance with this invention exhibits characteristics similar to those of a new pavement. The pavement regains its ability to heal cracks under traflic and previously curled surfaces flatten under trafiic; it' regains its cold-flow properties. Advantageously the composition of this invention may be used to renew aged pavement even when an overlayer is to be applied as treatment with the novel composition has been found to increase the binding action between the existing pavement and the new surface.

The novel composition is preferably applied to the pavement at the rate of about 0.05 to 0.5 gallons per square yard. Less seems to be insufficient to adequately rejuvenate the pavement and more may cause the pave ment to become unstable. Conventional methods of handling liquid bituminous material can be used in applying the composition to the paving, such, for example, as by spraying.

After the novel composition is applied to the paving, it is permitted to soak for a short period, for example, a half hour. Then, the surface is brushed with a stiff broom to remove any excess composition from low areas and deposit it in the cracks. Thereafter, the paving is ready for the movement of rubber-tired vehicles thereover. With time, the bituminous pavement rej'uvenator plasticizes the old bituminous pavement and softens the material in the vicinity of the cracks to the extent that rubber-tired trafiic will close the cracks. In areas such as airports Where the vehicular trafiic may be small, it is desirable to roll the rejuvenated bituminous paving with a rubber-tired roller.

The novel rejuvenating composition of this invention continues to penetrate into the paving for a substantial period of time. The extent of penetration may readily be determined visually since the portion which has been penetrated by the novel rejuvenating composition has a color that is darker than that of the aged pavement. This penetration appears to be a direct function of the length of time after application. The chart, FIGURE 2, shows, for example, the depth of penetration in inches of an asphalt concrete pavement as a function of time, the determination having been made by drilling a core. from the pavement at various intervals of time.

The novel composition restores or enhances the previous characteristics. The extent of the plasticizing of the paving can be conveniently illustrated by the use of the characteristic of a bituminous paving material known as penetration. Penetration (ASTM D 5-25) is determined by measuring the distance in tenths of a millimeter that a needle penetrates into the asphalt under controlled conditions. A series of weathered asphalt paving was tested as to penetration after the addition of the novel rejuvenating composition of this invention to the paving at various rates of application. It again is evident that the plastifying of the aged paving is a direct function of the amount of rejuvenating composition added to'the pavement. The results of the tests are illustrated in FIGURE 3. e

The specifications for a typical rejuvenating composition of this invention are as follows:

Test Methods Characteristic ASTM:

D-1298 Spcific Gravity at 25/25 1.08 min. D-974 Acid Number 1.0-8.0.

BIOOkllCd Viscosity 1 at 30 cps. max.

25 D-4 Soluble in CS by wt 95 min.

Flash Point (3.0.0. F 200 min. Ditillation Curve to 300 Initial Boiling Point 180 C. min. Temperature, 0.: Distillate (percent by volume of total composition) 1.0 max. 2.0 max. 3.0 max. 4.0 max. 5.0 max 0.0 max 10.0 max 2-18. 5-30. 15-40. 20-45. 25-55. 300 30-60. D-1298 Specific Gravity at 25/25 1.025 min C. Distillate to 300 C. D-88 SSF Viscosity at 122 F. 120 max Residue above 300 C.

1 INF Model-No. 1 spindelspeed 30-Factor 2.

The distillation characteristics of the novel composition of this invention are illustrated diagrammatically in FIGURE 1.

The novel composition above is derived from the distillation of coal tar. An infra-red analysis of the composition shows the following compounds to be present: naphthalene, alpha-beta-methylnaphthalene, diphenyl, dimethylnaphthalene, acenaphthene, diphenyloxide, fluorene, phenanthrene, carbazole, fluoranthrene, pyrene and chrysene.

In rejuvenating an aged bituminous paving, the composition is applied to the paving advantageously by spraying at a rate, for example, of 0.1 gallon per square yard. The composition is permitted to soak for one-half hour and thereafter distributed further over the surface by brushing with a stiff broom. This also has the advantage of flowing in a liquid material into the cracks of the paving. When traffic is to proceed immediately over the paving, it is desirable to sprinkle the paving with sand so as to minimize pick-up of the rejuvinating composition on the tires of the cars. If the traffic is not heavy, it is advantageous to roll the paving at the end of sixty days with a roller having rubber tires. The rejuvenator gives the aged paving a new dark coloration so that the paving appears to have been newly laid. In addition, it restores the cold flow properties and flexibility to the paving so that it behaves in the manner of a new paving.

It is, of course, not necessary to wait until the bituminous paving has aged to the extent that it cracks and ravels before applying the novel composition of this invention thereto. The composition is usable both in the preventive maintenace of bituminous paving and in the corrective maintenance of bituminous paving. In preventive maintenance, the novel composition is applied to the paving before there is feasible evidence of pitting or cracking but when, due to age or other factors, there is a suspicion that the paving will deteriorate soon. In corrective maintenance, the novel rejuvenating composition is applied to the aged bituminous paving after it has reached a substantial state of deterioration. In either case, the novel composition revitalizes the aged paving so as to extend its useful life.

The foregoing has presented a novel composition and method of rejuvenating asphalt pavements. It is particularly advantageous for use on a city street where decreasing curb heights inhibit the use of additional pavement overlays unless new curbs are placed or unless the present pavement is removed to some depth. Other applications, of course, include the pretreatment of cracked pavements prior to overlaying with new bituminous courses so that the cracks in the old pavement will not be reflected up to the new overlay. It can also be used to pretreat pavement surfaces for planing operations with a conventional heater-planer, or to pretreat pavement prior to heating with conventional infra-red equipment used for healing cracks.

I claim:

1. A composition for rejuvenating asphalt paving comprising a mixture of di-, triand tetracyclic aromatic compounds and their alkyl homologs containing lower alkyl groups together with a significant amount of phenolic and hydroxy derivatives, said mixture being derived from the distillation of coal tar, said mixture having a specific gravity of 25/25 C. of at least 1.08, a maximum Brookfield viscosity at 25 C. of 30 cps., and an initial boiling point of at least C. and a continuous boiling range to at least 300 C., 70-40% by volume of the material remaining as residue at 300 C. with a distillation curve to 300 C. of

Distillate (percent by volume Temperature, C.: of total composition) said distillate to 300 C. having a minimum specific gravity at 25/25 C. of about 1.025 and said residue having a maximum S.S.F. viscosity at 122 F. of 120.

2. A method of rejuvenating aged bituminous paving which comprises applying to the paving at a rate of 005-05 gallon per square yard a composition comprised of a mixture of di-, triand tetracyclic aromatic compounds and their alkyl homologs containing lower alkyl groups together with a significant amount of phenolic and hydroxy derivatives said mixture being derived from the distillation of coal tar, said mixture having a specific gravity at 25/25 C. of at least 1.08, a maximum Brookfield viscosity at 25 C. of 30 cps. and in initial boiling point of at least 180 C. and a continuous boiling range to at least 300 C., 70-40% by volume of the material remaining as residue at 300 C. with a distillation curve to 300 C. of

Distillate (percent by volume Temperature, C.: of total composition) 180 1.0 max. 2.0 max. 200 3.0 max. 210 4.0 max.

220 5.0 max. 230 6.0 max. 240 10.0 max. 250 2-18 260 5-30 said distillate to 300 having a minimum specific gravity at 25/25" C. of about 1.025, said residue having a maximum S.S.F. viscosity at 122 F. of 120- so that said composition will penetrate said paving.

References Cited by the Examiner UNITED STATES PATENTS Wallace 94-23 Robinson 106279 X Burgin 106-379 X Wells 94-23 Scott 9423 Neville 9423 Roberts 94-50 6 3,072,559 1/:1963 Corbett 20833 3,162,101 12/1964 Rostler 94-23 OTHER REFERENCES 5 SN. 245,735, Horn (A.P.C.), published April 1943. Chemistry of Coal Utilization by Lowry vol. 2 pages 1292, 1293, 1325, 1326, 1327 published by Wiley N. Y. Asphalts and Allied Substances by Abraham 5th Edi tion v01. -1, pages 529 and 530 published in 1945 by 10 P. Van Nostrand Co. N. Y.

CHARLES E. OCONNELL, Primary Examiner. JACOB L. NACKENOFF, Examiner. 

1. A COMPOSITION FOR REJUVENATING ASPHALT PAVING COMPRISING A MIXTURE OF DI-, TRI- AND TETRACYCLIC AROMATIC COMPOUNDS AND THEIR ALKYL HOMOLOGS CONTAINING LOWER ALKYL GROUPS TOGETHER WITH A SIGNIFICANT AMOUNT OF PHENOLIC AND HYDROXY DERIVATIVES, SAID MIXTURE BEING DERIVED FROM THE DISTILLATION OF COAL TAR, SAID MIXTURE HAVING A SPECIFIC GRAVITY OF 25/25*C. OF AT LEAST 1.08, A MAXIMUM BROOKFIELD VISCOSITY AT 25*C. OF 30 CPS., AND AN INITIAL BOILING POINT OF AT LEAST 180*C. AND A CONTINUOUS BOILING RANGE TO AT LEAST 300*C., 70-40% BY VOLUME OF THE MATERIAL REMAINING AS RESIDUE AT 300*C. WITH A DISTILLATION CURVE TO 300*C. OF 